1813.] Anahjsis of Graphite, 295 



graphite reduced to a fine powder in a sufficient quantity of 

 water. The liquid treated with acetate of barytes yielded ^ oi 

 a grain of sulphate of barytes, which may be considered as 

 equivalent to -pV^^ ^ grain of sulphate of iron.* 



2. The graphite tlius boiled in water was burnt in a silver 

 crucible with 10 times its weight of saltpetre. The combustion 

 always took place after the mass had continued for some time 

 red hot. The residuary mass, after the salt had been washed off 

 by water, weighed ]6'2 grains^ and was a light reddish grey 

 powder. The saline ley was evaporated to dryness, again dis- 

 solved in vvater, saturated with an acid, and evaporated a second 

 time. By this treatment some silica separated. Carbonate of 

 soda separated ^Vths of a grain of alumina. 



3. The grey powder was boiled in nit ro- muriatic acid, which 

 assumed in consequence a yellovv^ colour. There separated from 

 this solution a white precipitate, which swam in curds in the 

 liquid, and which when strongly dried weighed 6*2 grains. 



4. The yellow solution, which by dilution with water had let 

 fall a white powdery precipitate, was super-saturated with caustic 

 ammonia, and the solution evaporated. No distinct blue colour 

 appeared. The liquid was mixed with car])onate of soda, and ex- 

 posed to heat till the whole of the ammonia was driven otT. The 

 salt thus obtained being dissolved in water, left a greyish green 

 residue, part of which was taken up by ammonia; and from that 

 solution prussiate of potash threw down a brownish red precipi- 

 tate, indicating clearly the presence of copper. 



5. The ferruginous precipitate obtained in paragraph 4, was, 

 while still moist, boiled in a dilute alkaline ley, by which 1*6 

 grain of alumina was separated. The oxide of iron, being well 

 washed, and heated with oil, gave 5-D grains of iron completely 

 attracted by the magnet. 



G. I took it for granted that the silica, whose existence in 

 gra])hite I had already ascertained by previous experiments, 

 would be found in the 6-2 grains, Vv'hich separated in paragraph 

 3, and in the powder which fell from the ferruginous solu^tion. 

 These were accordingly mixed with an alkaline ley in a platinum 

 crucible, and exposed to a red heat. The mass was completely 

 dissolved in water. It was saturated with muriatic acid, and 

 again evaporated. Instead of leaving, as is usual when silica is 

 present, a gelatinous mass belli nd, a fine sandy precipitate sepa- 

 rated, which being examined by a magnifying glass appeared to 

 consist of small crystals. This sandy precipitate was dissolved in 

 soda ley without the assistance of heat, and the solution assumed 

 a slightly brown colour. The ley was saturated with muriatic 

 acid, and evaporated. The silica now separated in the form of a 

 jelly ; and the filtered solution, when treated with prussiate of 



* A hundred grains of crystallized sulphate of iron yielded, Aihcn precipi- 

 atgd by mariate of barytes, 83 T grains of sulphaie of barytes. 



